There are several reasons that ink-jet printing has become a popular way of recording images on various media surfaces, particularly plain paper. Some of these reasons include low printer noise, capability of high-speed recording, and multi-color recording. Additionally, these advantages can be obtained at a relatively low price to consumers. However, though there has been great improvement in ink-jet printing, accompanying this improvement are increased demands by consumers in this area, e.g., higher speeds, higher resolution, full color image formation, increased stability, higher image quality, etc.
As new ink-jet inks are developed, there are several traditional characteristics that are considered when evaluating the ink for use in conjunction with a printing surface or other inks. Such characteristics include edge acuity and optical density of the image on the surface, black to color bleed control, black to color wicking, halo control, dry time of the ink on the substrate, adhesion to the substrate, lack of deviation in ink droplet placement, presence of all dots, acceptable slewing decap time, resistance of the ink after drying to water and other solvents, long term storage stability, and long term reliability without corrosion or nozzle clogging. Though the above list of characteristics provides a worthy goal to achieve, there are difficulties associated with satisfying all of the above characteristics. Often, the inclusion of an ink component meant to satisfy one of the above characteristics can prevent another characteristic from being met. Thus, most commercial inks for use in ink-jet printers represent a compromise in an attempt to achieve at least an adequate response in meeting all of the above listed requirements.
One problem associated with reduced line quality and accuracy of plots of certain pigment-based ink-jet inks is directly related to a problem known as capping or decap. The term “decap” is meant to be understood both here and in the appended claims as referring to the inability of an ink-jet ink to remain fluid upon exposure to air that would lead to degradation of print quality. To avoid the problems associated with decap, ink-jet architecture or pens are fired periodically at times other than when printing on a desired substrate, resulting in wasted ink-jet ink. The time between two firings is called slewing time. Thus, by increasing slewing time, less ink-jet ink is wasted and the ink-jet printer and ink-jet printing architecture or pen does not have to work as hard therefore the throughput can be improved. One method of increasing slewing time that is known in the prior art is to increase the kinetic energy of the drop ejected from the pen. However, increasing the kinetic energy also tends to increase the spray, drop weight, and/or other image quality degrading characteristics. Certain types of pigments that are otherwise very good with respect to print quality, e.g., low bleed, low wicking, low halo, fast throughput, excellent line quality, etc., often have unacceptably low slewing time. When the slewing decap time is very short, heavy spitting is required to maintain good print quality which would greatly reduce printer's throughput. Thus, it would be beneficial to provide pigment-based ink-jet ink formulations that have long slewing decap time.